A better approach might be to add this as a contributed .thrift file for the contrib/ directory, with associated per-language library files.
The wire format certainly would need to be timezone invariant (like epochtime) and probably less limited than epochtime (dates before Jan 1, 1970 have been known to happen). As a subdirectory in contrib/, it would be a convenient and safe place to stomp out the platform/timezone/precision/dependency/language-nativetype-mapping bugs. If it goes well, it would certainly be useful for functionality and as an example. Just my $0.02.
